Composition of magnesium carbonate

　　Basic magnesium carbonate has many components, and its composition is generally expressed in xMgCO3·yMg(OH)2·zH2O[1]. Among them, there are several ratios of x, y and z, which can be 4:1:4, 4:1:5, 4:1:6, 4:1:7, 3:1:3, 3:1:4 and so on. Basic magnesium carbonate is a white crystalline or amorphous powder, non-toxic, odorless, stable in air; Slightly soluble in water, the aqueous solution is weakly alkaline, easily soluble in acid and ammonium salt solutions; In case of dilute acid, carbon dioxide is liberated; Heated above 300 °C, it decomposes to produce water, carbon dioxide and magnesium oxide.

　　Basic magnesium carbonate is very widely used, mainly used in rolling rubber, rubber, dyes, paints, electronics, medicine, food, flour improvers and other industries, is a good desiccant, wear-resistant and insulation materials, and is one of the raw materials for the preparation of high purity magnesium oxide.

　　After the soluble magnesium salt and carbonate are mixed, basic magnesium carbonate can be obtained under certain conditions. Generally, the sedimentary volume (bulk density) of basic magnesium carbonate and the content of magnesium oxide are obtained after the reaction to measure whether the product is heavy or light. Heavy magnesium carbonate is commonly used in the food, cosmetics and pharmaceutical industries. The sedimentary volume of light magnesium carbonate is generally required to be 6-7ml/g, and the sedimentary volume of heavy magnesium carbonate is less than 1.5ml/g. That is to say, the larger the sedimentary volume, the finished product tends to be lightweight.

　　Generally 3MgCO3 · Mg(OH)2·3H2O stands for lightweight magnesium carbonate, with 3MgCO3· Mg(OH)2·4H2O、4MgCO3· Mg(OH)2·4H2O[5] stands for heavy magnesium carbonate. The content is calculated according to magnesium oxide (MgO), and the heavy magnesium carbonate should be 40.0% to 43.5%.